A typical vane-type camshaft phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to one of the advance and retard chambers and vacated from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between an engine camshaft and an engine crankshaft. Camshaft phasers also commonly include two intermediate lock pins which selectively prevent relative rotation between the rotor and the stator at an angular position that is intermediate of a full advance and a full retard position. One example of such a camshaft phaser is described in United States Patent Application Publication number US 2009/0266322-A1. In this example, a primary lock pin is selectively seated in a primary lock pin seat which is elongated to allow relative rotation between the rotor and the stator in a range that is between full advance and full retard. The secondary lock pin is selectively seated in a secondary lock pin seat in order to substantially prevent relative rotation between the rotor and the stator at a predetermined position that is within the range. The primary lock pin assists in engagement of the secondary lock pin with the secondary lock pin seat by limiting rotation of the rotor to a small range when the primary lock pin is seated in the primary lock pin seat. With the primary lock pin constraining rotation of the rotor to a small range, it is easier to precisely align the secondary lock pin with the secondary lock pin seat which fit together very closely in order to substantially prevent relative rotation between the rotor and the stator.
Now referring to FIG. 1, it is known to use pressurized oil from the internal combustion engine to disengage the primary and secondary lock pins from the primary and secondary lock pin seats respectively. Pressurized oil is supplied to annular groove 10 of camshaft 12. Primary lock pin camshaft oil passage 14 extends axially into camshaft 12 and is in fluid communication with annular groove 10 through primary lock pin camshaft connecting passage 16 which extends radially into camshaft 12. Primary lock pin camshaft oil passage 14 is aligned with primary lock pin rotor oil passage 18 which extends axially into rotor 20. Primary lock pin rotor oil passage 18 is in fluid communication with primary lock pin 22 through primary lock pin rotor connecting passage 24 which extends radially into rotor 20. Similarly, secondary lock pin camshaft oil passage 26 extends axially into camshaft 12 and is in fluid communication with annular groove 10 through secondary lock pin camshaft connecting passage 28 which extends radially into camshaft 12. Secondary lock pin camshaft oil passage 26 is aligned with secondary lock pin rotor oil passage 30 which extends axially into rotor 20. Secondary lock pin rotor oil passage 30 is in fluid communication with secondary lock pin 32 through secondary lock pin rotor connecting passage 34 which extends radially into rotor 20.
While this arrangement of one axial lock pin oil passage in the camshaft for each lock pin may be satisfactory for some applications, it may be unsatisfactory for other applications. For example, an internal combustion engine manufacturer that had previously employed a camshaft phaser with a single lock pin, and consequently only one axial lock pin oil passage in the camshaft for communication with the lock pin, may wish to switch to a camshaft phaser with a dual lock pin arrangement. A redesign of the camshaft would be required to include a second axial lock pin oil passage in the camshaft in order to accommodate the second lock pin of the camshaft phaser. This redesign may be costly and time intensive.
This arrangement of one axial lock pin oil passage in the camshaft for each lock pin may also be unsatisfactory for some applications due to a limited availability of space in the camshaft. More specifically, the camshaft may include a plurality oil passages for supplying oil to and from the advance and retard chambers of the camshaft phaser. This plurality of oil passages for supplying oil to and from the advance and retard chambers may leave insufficient space for multiple axial lock pin oil passages in the camshaft.
What is needed is a camshaft phaser having primary and secondary lock pins and a single hydraulic interface with the internal combustion engine for communication of oil to and from both the primary and secondary lock pins. What is also needed is such a camshaft phaser which includes a rotor and a cap disposed axially adjacent to the rotor to define a lock pin passage therebetween which provides fluid communication between the primary and secondary lock pins.